1. The Field of the Invention
The present invention relates to optical devices and to optical devices that include features for increasing the surface warp resistance of the optical devices.
2. Background
Fiber optic technology is increasingly employed in the transmission of data over communication networks. Networks employing fiber optic technology are known as optical communication networks, and are typically characterized by high bandwidth and reliable, high-speed data transmission.
To communicate over an optical communication network using fiber optic technology, fiber optic components such as fiber optic transceivers or transponders are used to send and receive optical signals. Generally, a fiber optic transceiver includes one or more optical sub-assemblies (“OSAs”) having an optical transducer. For example, transmitter optical sub-assemblies (“TOSAs”) have an electro-optical transducer for sending optical signals, and receiver optical sub-assemblies (“ROSAs”) have an optoelectronic transducer for receiving optical signals. More particularly, a TOSA receives an electrical data signal and converts the electrical data signal into an optical data signal for transmission onto an optical network. A ROSA receives an optical data signal from the optical network and converts the received optical data signal to an electrical data signal for further use and/or processing. Both the ROSA and the TOSA include specific optical components for performing such functions.
For example, a typical TOSA includes an optical transmitter such as a light emitting diode or a laser diode for transmitting an optical signal to an optical fiber or optical waveguide. The optical transmitter is typically covered by an at least partially transparent cap that protects the optical transmitter while allowing the optical transmitter to transmit the optical signal to the optical cable. The cap may include a lens for focusing the optical signal transmission.
A typical ROSA includes an optical receiver, such as a PIN photodiode or avalanche photodiode (“APD”). The optical receiver is typically covered by an at least partially transparent cap that protects the optical receiver and allows the optical receiver to receive an optical signal from an optical cable. The cap may include a lens for focusing the optical signal transmission received from the optical cable.
The lens and other optical components are often press fit into the corresponding OSA. When an optical component is press fit to a holder, the compression force may alter the surface profile of the optical component. This may be especially significant if the optical component uses soft or deformable material, such as plastic. Further, while the OSA is operating the optical components may be subjected to large amounts of thermal energy. The thermal energy causes the optical component to expand relative to the holder, resulting in compressive forces on the optical component due to differences in the coefficients of thermal expansion (CTE) of the holder and the optical component, which may result in stress on the surfaces of the optical component. Stress on the surfaces of the optical component may result in a change in the reflective index and/or birefringence of the materials. Such changes may interfere with the efficient operation of the optical component by changing the focus spot size, the position of the image and/or the quality of the image.
Previous attempts to reduce stresses on the surfaces of optical components due to press fitting and/or thermal expansion have included the use of a holder and optical component with similar CTEs. Such approaches are often impractical as such material may have been difficult to obtain and/or the material selection may have been at least partially constrained by the product specifications. Other attempts have included using compliant adhesive materials to bond the optical component to the holder. Such approaches may be costly due, at least in part, to additional process steps and additional costs associated with obtaining and using the materials.